#include <iostream>
using namespace std;

class Circle {
	private:
		double radius;
	public:
		Circle(double r): radius(r) {}
		friend double calculateArea(Circle c);
};

double calculateArea(Circle c) {
	return 3.14 * c.radius * c.radius;
}

int main() {
	Circle circle(5);
	std::cout << "Area: " << calculateArea(circle) << std::endl;
	return 0;
}